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An idea that comes to my mind to swing a baby swing automatically is using a CD drive eject - close function , I have several such drives I dont use and I dont want to use a computer to do the periodic control eject \ close. Can I attach an auxiliary circuit which just helps in periodic open-close motion of the CD drive. Also, are there any other ways to make the swing automatic , what I need is just a backforth motion to couple it with the swing?

The major requirement is high torque high amplitude swinging which the modern fisherprice swings lack and babies love.

weight : should withstand 1 to 12 Kg babies

Could be used with any normal swing to convert it to auto swinging with all safety aspects fulfilled.

Here is the typical swing:

enter image description here

Note: Some babies wont just sleep unless they are swinged continuously hence the question.

Note : CD room requirement is no longer valid.

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    \$\begingroup\$ A cd drive ejector stalls easily. It does not have the strength to move a steady hand, let alone a baby. \$\endgroup\$
    – Passerby
    Oct 21, 2013 at 10:57
  • \$\begingroup\$ @Passerby suspension of baby on the swing is the key \$\endgroup\$
    – elex101
    Oct 22, 2013 at 8:47
  • \$\begingroup\$ *thinks of Rube Goldberg* \$\endgroup\$
    – Daniel
    Oct 15, 2015 at 1:25

4 Answers 4

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Well, you probably can. Simply create some very slow generator (based on 555) and connect some relay in parallel with the eject button of the CD drive.

But isn't usual CD drives too noisy for such application? And how long the drive mechanic will live with such big mechanical loads?

Instead of using CD Drive, some small motor with gearbox seems to be a better solution for me. The motor need to have 20..30..50rpm output speed. Some of these may fit, but there are thousands of them in the on-line shops.

The needed speed depends on what the baby prefer.

Just put a disk on the output shaft and tiе a rubber band at the disk periphery. The other end of the band tie to the baby swing. In this construction only ON/OFF and optionally motor speed control is needed. The swinging will be generated by the mechanic. Here is very raw drawing of what I mean:

enter image description here

Very small motor is needed, because the swing will be accelerated smooth in the time. Some adjustment of the motor speed might be needed in order to work in the resonance frequency of the swing. Count the swings per minute of the swing and search for the same rpm motor. Some variable voltage power source will make such adjustments easy.


Safety:

The maximal amplitude of the swing must be limited in some way. If because of some reason, the elastic band is winded on the shaft, something must stop the swing and cause the band to be broken or the motor stalled, but not the swing torn down. Make the extended tests without your baby in the swing, but some heavy enough object instead.

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  • \$\begingroup\$ Also, are there any other ways to make the swing automatic , what I need is just a backforth motion to couple it with the swing? \$\endgroup\$
    – elex101
    Oct 21, 2013 at 7:54
  • \$\begingroup\$ If you are seeking clarification or commenting on the question, that belongs as a comment post on the question. If you are answering the OP's question, then "some very slow generator" and the general hand-waving is a really poor example of an answer. \$\endgroup\$ Oct 21, 2013 at 7:54
  • \$\begingroup\$ @AnindoGhosh - I don't need clarification. The question is clear and my answer is about how to implement what the elex101 wants. "very slow generator" is because the needed frequency may varies with the baby - some like it slow, some faster. \$\endgroup\$
    – johnfound
    Oct 21, 2013 at 8:00
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    \$\begingroup\$ @AnindoGhosh - Internet is full of 555 schematics. If you can't search in it - it is not my problem. \$\endgroup\$
    – johnfound
    Oct 21, 2013 at 8:07
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    \$\begingroup\$ @johnfound My downvote is for the vague hand-waving in the first paragraph. \$\endgroup\$ Oct 21, 2013 at 10:09
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The baby swing is a pendulum which will have a natural frequency of oscillation only dependent on the distance from the centre of rotation to the centre of gravity of the baby and carrier. This may vary with baby's position. If the swing is nudged at the correct frequency the oscillations will increase in amplitude until friction counters the applied force.

I suggest a variable speed motor and gearbox with an eccentric pusher to nudge the rope every cycle. Once the swing reaches a certain oscillation amplitude the pusher will lose contact so it's self-limiting. To set up, push the swing and measure it's natural frequency of oscillation. Set the motor speed to match.

enter image description here

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  • \$\begingroup\$ Nice idea , can you link to some practical motor \$\endgroup\$
    – elex101
    Oct 18, 2015 at 15:12
  • \$\begingroup\$ Also how can it be setup for the swing shown in the question. Will this give high amplitude swing ? \$\endgroup\$
    – elex101
    Oct 18, 2015 at 15:16
  • \$\begingroup\$ @elex101: Looking at my sketch, you can set the amplitude by 1) moving the motor-gearbox closer to the rope pivot for a larger amplitude, etc., or 2) move the pusher further from the gearbox centre for the same result. If the system works you will initially see a bend in the rope as sketched but when swinging gets going it should, ideally, form a straight-line tangent to the pusher. \$\endgroup\$
    – Transistor
    Oct 18, 2015 at 18:22
  • \$\begingroup\$ @elex101: You could start off by trying to source a car wiper or window winder motor assembly and a variable voltage DC power supply 0 - 12 V at 1 - 2 A might be enough. \$\endgroup\$
    – Transistor
    Oct 18, 2015 at 18:29
  • \$\begingroup\$ @elex101: If you find a fixed speed motor / power supply close to what you require you could adjust the length of the swing ropes to match the actuator and swing. See Wikipedia's pendulum article for a formula. \$\endgroup\$
    – Transistor
    Oct 18, 2015 at 20:24
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You can use Arduino, and use the code from this site:

http://singlevalve.web.fc2.com/Atapiduino/atapiduino.htm

Make a loop that will keep sending the eject/close command.

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  • \$\begingroup\$ thanks but I dont want to invest in using arduino or any controller, I believe this can be accomplished by a simple circuit. \$\endgroup\$
    – elex101
    Oct 21, 2013 at 7:43
  • \$\begingroup\$ Well, you can hack the CDROM eject button, if you want to. Solder a wire to the button, then connect the wire to relay. Use 555 timer with small "on" time, each time the "on" is triggered, your relay will connect, and will simulate the pressing of the button \$\endgroup\$ Oct 21, 2013 at 7:47
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    \$\begingroup\$ -1 for unnecessary & gratuitous arduino usage. \$\endgroup\$
    – John U
    Oct 21, 2013 at 8:50
  • \$\begingroup\$ @JohnU, the poster did not mention that he did not want to use Arduino, so suggesting using Arduino is one of the possible answer. He is free to accept or not the answer. Thanks. \$\endgroup\$ Oct 21, 2013 at 9:39
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    \$\begingroup\$ @JohnU your comment clearly shows you dinged the post because of Arduino usage. The solution itself is not practical so I will not upvote it, I don't believe a CD ROM eject motor can move the weight of an average-sized plump baby, regardless of what circuitry drives it. And no, this site is not about downvoting anything Arduino. \$\endgroup\$
    – Ron J.
    Oct 21, 2013 at 13:06
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In order to respond to your update,
an option with a simple circuit that opens and closes the drive periodically can easily be made by a switch reversing the polarity of the current fed to the motor. You can see a good explanation for this in the following youtube video for example, where someone presents how to make a crawlworm bot from a CD drive:
https://www.youtube.com/watch?v=pKIG4uJBIsQ

Depending on your swing, you can easily attach it to one of the legs at a height corresponding to the amplitude you want the baby to swing at.

There are two drawbacks for this approach:
1. as stated by other users before, the motor will most likely not be strong enough (you can block a CD drive opening with your hand easily)
2. this setup only allows to open at close at a single frequency, given by the motors speed. You could adjust voltages to tune this, but I am not sure to which extend this works out.

Good luck

/edit: A combination of this approach and the elastic band option might be powerful enough in time to get a swinging motion going. Don't forget to limit the motion, though.

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